The GOP message of fiscal prudence and pro-growth policies is hitting home with voters tired of the status quo.

In a scene reminiscent of “Weekend at Bernie’s,” Hillary Clinton, Elizabeth Warren and a retinue of other Democratic celebs gathered on Friday to prop up Martha Coakley’s ailing campaign for Massachusetts governor, at Boston’s Park Plaza Hotel. The place is a classic Roaring ’20s pile, with an “imperial ballroom” featuring three-story vaulted arches and Baccarat crystal chandeliers—which made it an ironic venue for accusations that Ms. Coakley’s rival, Charlie Baker, is attempting to buy the Massachusetts Statehouse.